The present invention relates generally to delivery and recovery devices for use in conjunction with specialized medical devices, such as an embolic filter used when an interventional procedure is being performed in a stenosed or occluded region of a body vessel to capture embolic material that may be created and released into the vessel during the procedure. The present invention also can be used to deliver other self-expanding medical devices, such as a self-expanding stent, within a patient's vasculature.
Numerous procedures have been developed for treating occluded blood vessels to allow blood to flow without significant obstruction. Such procedures usually involve the percutaneous introduction of an interventional device into the lumen of the artery, usually through a catheter. One widely known and medically accepted procedure is balloon angioplasty in which an inflatable balloon is introduced within the stenosed region of the blood vessel to dilate the occluded vessel. The balloon catheter is initially inserted into the patient's arterial system and is advanced and manipulated into the area of stenosis in the artery. The balloon is inflated to compress the plaque and press the vessel wall radially outward to increase the diameter of the vessel, resulting in increased blood flow. The balloon is then deflated to a small profile so that the dilatation catheter can be withdrawn from the patient's vasculature. Enhanced blood flow should now resume in the dilated artery. As should be appreciated by those skilled in the art, while the above-described procedure is typical, it is not the only method used in angioplasty.
In the procedure of the kind referenced above, abrupt reclosure may occur or restenosis of the artery may develop over time, which may require another angioplasty procedure, a surgical bypass operation, or some other method of repairing or strengthening the injured area. To reduce the likelihood of the occurrence of abrupt reclosure and to strengthen the area, a physician can implant an intravascular prosthesis for maintaining vascular patency, commonly known as a stent, inside the artery across the lesion. The stent can be crimped onto the balloon portion of the catheter and transported in its delivery diameter through the patient's vasculature. At the deployment site, the stent is expanded to a larger diameter, often by inflating the balloon portion of the catheter.
A variety of stent designs have been developed and include self-expanding stents insertable and deliverable through the patient's vasculature in a compressed state for deployment in a body. Unlike balloon expandable stents which rely on an external radial force to expand the stent at the area of treatment, self-expanding stents are made from materials which are self-expanding in order to move between a compressed or collapsed position to an expanded, implanted position. Stent delivery catheters used for implanting self-expanding stents usually include an inner member upon which the compressed or collapsed stent is mounted and an outer restraining sheath placed over the stent to maintain it in its compressed state prior to deployment. When the stent is to be deployed in the body vessel, the outer restraining sheath is retracted in relation to the inner member to uncover the compressed stent, allowing the stent to move into its expanded condition for implantation in the patient.
These non-surgical interventional procedures, when successful, avoid the necessity of major surgical operations. However, there is one common problem associated with these procedures, namely, the potential release of embolic debris into the bloodstream that can occlude distal vasculature and cause significant health problems to the patient. For example, during deployment of a stent, it is possible for the metal struts of the stent to cut into the stenosis and shear off pieces of plaque which become embolic debris that can travel downstream and lodge somewhere in the patient's vascular system. Pieces of plaque material can sometimes dislodge from the stenosis during a balloon angioplasty procedure and become released into the bloodstream. Angioplastic procedures which are performed in occluded saphenous vein grafts, implanted as a result of an open heart surgical procedure, pose a particularly difficult problem to the physician since a large amount of embolic debris is usually generated during the angioplasty procedure.
When any of the above-described procedures are performed in the carotid arteries, the release of emboli into the circulatory system can be extremely dangerous and sometimes fatal to the patient. Debris that is carried by the bloodstream to distal vessels of the brain can cause these cerebral vessels to occlude, resulting in a stroke, and in some cases, death. Therefore, although cerebral percutaneous transluminal angioplasty has been performed in the past, the number of procedures performed has been limited due to the justifiable fear of causing an embolic stroke should embolic debris enter the bloodstream and block vital downstream blood passages.
Medical devices have been developed to attempt to deal with the problem created when debris or fragments enter the circulatory system during vessel treatment. One technique which has had some limited success include the placement of a filter or trap downstream from the treatment site to capture embolic debris before it reaches the smaller blood vessels downstream. The placement of a filter in the patient's vasculature during treatment of the vascular lesion can reduce the presence of the embolic debris in the bloodstream. Some prior art expandable filters are attached to the distal end of a guide wire or guide wire-like member that allows the filtering device to be placed in the patient's vasculature. The guide wire allows the physician to steer the filter to a downstream location from the area of treatment. Once the guide wire is in proper position in the vasculature, the embolic filter can be deployed to capture embolic debris. These embolic filtering devices usually utilize a restraining sheath to maintain the expandable filter in its collapsed position. Once the proximal end of the restraining sheath is retracted by the physician, the expandable filter will move into its fully expanded position. The restraining sheath can then be removed from the guide wire allowing the guide wire to be used by the physician to deliver interventional devices, such as a balloon angioplasty catheter or a stent delivery catheter, into the area of treatment. After the interventional procedure is completed, a recovery sheath can be delivered over the guide wire using over-the-wire techniques to collapse the expanded filter (with the trapped embolic debris) for removal from the patient's vasculature. Both the delivery sheath and recovery sheath should be relatively flexible to track over the guide wire and to avoid straightening the body vessel once in place.
While a filter can be effective in capturing embolic material, the filter still needs to be collapsed and removed from the vessel. During this step, there is a possibility that trapped embolic debris can backflow through the inlet opening of the filter and enter the bloodstream as the filtering system is being collapsed and removed from the patient. Therefore, it is important that any captured embolic debris remain trapped within this filter so that particles are not released back into the body vessel.
When a combination of an expandable filter and guide wire is utilized, it is important that the guide wire be rotatable so that the physician can steer it downstream of the area of treatment using techniques well known in the art. In this regard, the guide wire is usually “torqued” by the physician to point or steer the distal end of the guide wire into the desired body vessel. Often, when a restraining sheath is utilized, it can be difficult to properly turn the composite device to deliver the filter through the tortuous anatomy of the patient. Moreover, during delivery, it is imperative that the restraining sheath remain positioned over the collapsed filter, otherwise the filter could be deployed prematurely in an undesired location in the patient's anatomy. This occurrence can cause trauma to the walls of the patient's vasculature and would require the physician to re-sheath the expanded filter in order to further advance the filter into the desired area.
When a restraining sheath is utilized to deliver or recover an expandable filter in the patient's vasculature, the length of the sheath can sometimes be problematic to the physician as well. For example, when a full-length restraining sheath is used (i.e., a tubular sheath extending from the area of treatment to an area outside of the patient), the guide wire utilized must have an extended length to allow the sheath to be removed and advanced along the guide wire. As a result, additional medical personnel may be required to hold the guide wire in place when the restraining sheath is being removed to allow the interventional devices to be advanced over the guide wire. The same would be true when a full-length recovery sheath is being used to collapse the expanded filter for removal from the patient's vasculature. Moreover, when full-length sheaths are used for other delivery or recovery, more time is usually needed to remove or advance the sheath along the guide wire.
What has been needed are reliable delivery and recovery sheath which can be used with embolic filtering devices that minimize the above-mentioned incidents from ever occurring. These devices should be relatively easy for a physician to use and should provide an effective means for deploying the embolic filtering device into the desired area of the body vessel and retrieving the same device without releasing any captured embolic debris into the body vessel. Moreover, it would be advantageous if sheaths can be advanced and removed from the guide wire in relatively quick fashion. The inventions disclosed herein satisfy these and other needs.